package com.itheima.common.utils;

import java.io.IOException;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;

/**
 *	@author zangye03
 *	date Jul 17, 20213:10:02 PM
 *	Description	 
 *	显示格式:首页 上一页 1 2 3 4 5 ... 下一页 尾页
 */

public class NavigationTag extends TagSupport{
	static final long serialVersionUID = 2372405317744358833L;
	
	/**
	 * request中用于保持Page<E>对象的变量名,默认为"page"
	 */
	private String bean = "page";
	/**
	 * 分页跳转的url地址,此属性必需
	 */
	private String url = null;
	/**
	 * 显示页码数量
	 */
	private int number = 5;
	
	@Override
	public int doStartTag() throws JspException {
		JspWriter writer = pageContext.getOut();
		HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();
		Page page = (Page) request.getAttribute(bean);
		if (page == null)
			return SKIP_BODY;
		try {
			// 计算总页数
			int pageCount = page.getTotal() / page.getSize();
			if (page.getTotal() % page.getSize() > 0) {
				pageCount++;
			}
			writer.print("<nav><ul class=\"pagination\">");
			// 首页链接路径
			String homeUrl = append(url,"page",1);
			// 末页链接路径
			String backUrl = append(url,"page",pageCount);
			// 显示"上一页"按钮
			if (page.getPage() > 1) {
				String preUrl = append(url,"page",page.getPage() - 1);
				preUrl = append(preUrl,"rows",page.getSize());
				writer.print("<li><a href=\"" + homeUrl + "\">" + "首页</a></li>");
				writer.print("<li><a href=\"" + preUrl + "\">" + "上一页</a></li>");
			} else {
				writer.print("<li class=\"disabled\"><a href=\"#\">" + "首页</a></li>");
				writer.print("<li class=\"disabled\"><a href=\"#\">" + "上一页</a></li>");
			}
			/*
			 * 显示当前页面的前两页码和后两页码
			 * 若 1 则 1 2 3 4 5,若 2 则 1 2 3 4 5,若 3 则 1 2 3 4 5,
			 * 若 4 则 1 2 3 4 5,若 10 则 8 9 10 11 12
			 * int indexPage=(page.getPage()-2>0)?page.getPage()-2:1;
			 */
			int indexPage = 1;
			if(page.getPage() - 2 <= 0) {
				indexPage = 1;
			}else if(pageCount - page.getPage() <= 2) {
				indexPage = pageCount - 4;
			}else {
				indexPage = page.getPage() - 2;
			}
			for (int i = 1; i <= number && indexPage <= pageCount; indexPage++, i++) {
				if (indexPage == page.getPage()) {
					writer.print("<li class=\"active\"><a href=\"#\">"
							+ indexPage + "<span class=\"sr-only\">(current)</span></a></li>");
					continue;
				}
				String pageUrl = append(url,"page",indexPage);
				pageUrl = append(pageUrl,"rows",page.getSize());
				writer.print("<li><a href=\"" + pageUrl + "\">" + indexPage + "</a></li>");
			}
			// 显示"下一页"按钮
			if (page.getPage() < pageCount) {
				String nextUrl = append(url,"page",page.getPage() + 1);
				nextUrl = append(nextUrl,"rows",page.getSize());
				writer.print("<li><a href=\"" + nextUrl + "\">" + "下一页</a></li>");
				writer.print("<li><a href=\"" + backUrl + "\">" + "尾页</a></li>");
			} else {
				writer.print("<li class=\"disabled\"><a href=\"#\">" + "下一页</a></li>");
				writer.print("<li class=\"disabled\"><a href=\"#\">" + "尾页</a></li>");
			}
			writer.print("</nav>");
		} catch (IOException e) {
			e.printStackTrace();
		}
		return SKIP_BODY;
	}
	
	private String append(String url, String key, int value) {
		return append(url, key, String.valueOf(value));
	}
	
	/**
	 * 为url参加参数对儿
	 * @param url
	 * @param key
	 * @param value
	 * @return
	 */
	private String append(String url, String key, String value) {
		// 判断url是否为空,以及除去首尾空格是否为空
		if (url == null || url.trim().length() == 0) {
			return "";
		}
		/*
		 *  int indexOf(String str, int fromIndex): 
		 *  返回从 fromIndex 位置开始查找指定字符在字符串中第一次出现处的索引，
		 *  如果此字符串中没有这样的字符，则返回 -1。
		 */
		if (url.indexOf("?") == -1) {
			url = url + "?" + key + "=" + value;
		} else {
			// endsWith() 方法用于测试字符串是否以指定的后缀结束
			if (url.endsWith("?")) { 
				url = url + key + "=" + value;
			} else {
				url = url + "&amp;" + key + "=" +value;
			}
		}
		return url;
	}
	
	/**
	 * 为url添加翻页请求参数
	 * @param url
	 * @param pageContext
	 * @return
	 * @throws JspException
	 */
	private String resolveUrl(String url, javax.servlet.jsp.PageContext pageContext) throws JspException {
		Map params = pageContext.getRequest().getParameterMap();
		for (Object key : params.keySet()) {
			if ("page".equals(key) || "rows".equals(key)) {
				continue;
			}
			Object value = params.get(key);
			if (value == null) {
				continue;
			}
			if (value.getClass().isArray()) {
				url = append(url,key.toString(),((String[]) value)[0]);
			} else if (value instanceof String) {
				url = append(url, key.toString(), value.toString());
			}
		}
		return url;
	}

	public String getBean() {
		return bean;
	}

	public void setBean(String bean) {
		this.bean = bean;
	}

	public String getUrl() {
		return url;
	}

	public void setUrl(String url) {
		this.url = url;
	}

	public int getNumber() {
		return number;
	}

	public void setNumber(int number) {
		this.number = number;
	}

	public static long getSerialversionuid() {
		return serialVersionUID;
	}
	
}
